1. Field of the Invention
The present invention relates to devices for providing shock and vibration isolation. More specifically, the present invention relates to soft matrix magnetorhelogical mounts for shock and vibration isolation.
2. The Prior Art
Devices for providing shock and vibration isolation are known in the art. A vibration isolation system prevents one object from affecting another from equipment using active or passive technology. Such systems are used extensively to isolate machinery (industrial and marine), civil engineering structures (base isolation in building, bridges, etc.), and sensitive components from the foundation/base. Vibration isolation schemes are to 1) reduce the propagation of base vibration to the isolated object (machinery) and 2) abate the transmission of vibration energy of machinery to the base. Moreover, in vehicular/marine, some industrial machines (such as mechanical presses), as well as seismic applications, isolators are also expected to lower the impact of shock from base to isolated object or vice-versa.
With passive methods, isolation is achieved by limiting the ability of vibrations to be coupled to the item to be isolated. This is done using a mechanical connection which dissipates or redirects the energy of vibration before it gets to the item to be isolated. Passive methods sometimes involve electromechanical controls for adjusting the system, but the isolation mechanism itself is passive. Passive systems may use elastomeric (rubber) or metal spring elements, fluids, or negative-stiffness components.
One of the most basic passive isolators is a spring placed between the surface transmitting shock or vibration and the item to be isolated. The spring opposes the impulse on it and absorbs some energy as it deforms. A fluid or elastomeric element is added to the spring element for damping. A simple example is the shock absorber in a car. In this case, mechanical energy from the shock or vibration does work on the fluid and is converted to thermal energy in the fluid, reducing the amount of energy transmitted to the body of the car. Elastomers are rubber-like materials which absorb mechanical energy by deforming. Examples of elastomeric isolators are shock and vibration mounts for automobile engines, aircraft components, industrial machinery, and building foundations. Because rubber does not have the same characteristics in all directions, isolation may be much better in one axis than the others.
With active methods, equal but opposite forces are created electronically using sensors and actuators to cancel out the unwanted vibrations. As early as the 1950s, active vibration cancellation systems were being developed for applications like helicopter seats. Thus, active control systems specifically for vibration control have been around for over 40 years. In the precision vibration control industry, active vibration isolation systems have been available for nearly 20 years.
One of the attractive applications in the use of active vibration is in engine mounting concept. The standard approach is to isolate the engine and the transmission vibrations from the chassis with rubber or hydro mounts. The active system is always a compromise between the conflicting requirements of acceptable damping and good isolation.
A soft-matrix magnetorheological (SMMR) material consists of micron/nano-sized ferrous particles suspended in a soft-matrix base material. The ferrous particles are embedded in the soft matrix and aligned by an external magnetic field while the matrix is cured. Once the SMMR material is cured, the rheological change occurs when a magnetic field causes the ferrous particles to polarize, and to attract each other; thus, changing the stiffness of the SMMR material. As magnetic field strength increases, the dipole moment created within the embedded ferrous particles increases, therefore, the attraction between the embedded particles increases. As stronger attraction forces are produced with increasing external magnetic field strength, the suspended particles form stiffer structured chain/columns that increase the stiffness of the SMMR material.
According to the present invention, the matrix material can be any flexible material in which the iron particles can be embedded. Such materials include, but are not limited to, silicone, natural rubber, nitrile, neoprene, ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), fluorocarbon, viton, polybutadiene, fluorosilicone. Any compound of the listed materials can also be used as the matrix material. A controllable SMMR vibration isolation device can offer many advantages where vibration and shock isolation of mechanical systems with variable payload is critical. The presented devices can potentially be utilized in vertical support bushings, engine mounts, shock and vibration isolation in any mechanical system/structure, and sensitive equipment mounts that require shock and vibration isolation to improve their performance. Any system that is subjected to random disturbances can benefit from the proposed controllable shock and vibration isolator. The controllable SMMR devices presented in this invention can be used in conjunction with a feedback control system that ensures desired device response to a given vibration and shock input utilizing a control strategy.
The present invention can reduce and mitigate shock and vibration of a system that is subjected to variable loads. The invention can reduce the maximum transmitted acceleration, as well as, shift the natural frequency of a system under dynamic loads. Normally, when a load changes, a new shock and vibration isolator with certain stiffness properties is needed. The controllability feature of the present invention can eliminate the need for design of a new shock and vibration isolation device, when the payload of the system changes. The controllability of the present invention also eliminates the need for the design of a new shock and vibration isolation system, in case of a load change and the need for specific stiffness properties. Instead of a new design, the power input to the inventions can be varied to adjust the stiffness properties, which makes the invented devices extremely adaptable and reconfigurable.